1. Technical Field
The present disclosure relates to methods of manufacturing gates so as to prevent shorts between metal gates and contacts, and semiconductor devices having the same. The methods are compatible with and can be performed in conjunction with methods of forming a polysilicon resistor during a replacement metal gate process.
2. Discussion of the Related Art
Semiconductor devices, such as, for example, transistors, resistors, capacitors, and the like, can be accessed by one or more contacts to the devices. However, as circuit density increases, the risk of shorting between a gate and a contact, such as an interconnect to a source or drain, increases. In addition, a protective or blocking layer on a gate, such as a nitride layer, may be removed during a process, such as a light process, during which the metal forming the contact, such as a self-aligned contact (SAC), is deposited. As a result, a short between the metal gate and the SAC may occur.
Contact to gate shorting creates a short circuit in the semiconductor device that degrades the function of semiconductor device, resulting in, for example, yield loss. A short between a contact opening filled with metallic material and a gate may result in the loss of an entire chip.
In addition, certain sections of the metal gate formed of a first metal may include a blocking layer, while others, formed of second metal, are left exposed to cause shorting. For example, a center section of a metal gate may include a blocking layer, such as an oxide, while end portions of the metal gate are not under a blocking layer, leaving the end portions vulnerable to shorting due to contact with the metal forming the interconnect.
Accordingly, there exists a need for a process that results in a semiconductor device in which metal gates are sufficiently protected from contacting interconnects, such as SACs, thereby preventing unwanted shorts.
In addition, there also exists a need for a process and a structure which prevents the above-described shorting, and is also compatible with a replacement metal gate (RMG) process, wherein disposable polysilicon gates are replaced by metal gates having lower resistivity than the polysilicon material, and polysilicon remains in the portions of a substrate forming the resistors.